Life changes its surroundings. Beavers build dams that alter the course of rivers. Forests can feed thunderstorms with their moisture. And those changes can, in turn, create new habitats that allow for the evolution of new kinds of life. For my new “Matter” column in the New York Times, I discuss a hypothesis about a truly global act of bio-engineering that may have happened 700 million years ago. Sponges may have transformed the oceans, flushing them with oxygen. And thanks to that change, more complex animals were able to evolve. We may have sponges to thank for being here, in other words. You can read the whole thing here.

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3 thoughts on “Sponges: Planetary Engineers?”

Filling The Gap In The Fossil Record
ScienceDaily (May 8, 2009) — The Neoproterozoic interval of “hidden” evolution refers to a gap of unknown duration between the time when animals first evolved (uncertain) and the oldest known fossil or geochemical evidence of animals (latest Neoproterozoic, about 600-650 million years ago).

Neuweiler et al. now propose to fill this gap. They describe distinctive, microscopic features in early Neoproterozoic limestone (between 779 and 1083 million years old) from the Northwest Territories of Canada, consisting of highly structured zones with multi-generational arrays of carbonate minerals, secondary voids, and internal sediment. Today, such a texture develops when aragonite crystals precipitate on the decaying connective tissue (collagen) of sponges in sediment on the sea floor. …[snip] …

Ancient rock deposits, laid down between two massive ice ages, reveal the oldest known fossils for two types of single-celled creatures: Tube-shelled foraminifera and hairy, vase-shape ciliates.

Both closely resemble microbes living today. But the climate they lived in may have been quite different. The fossils appear in limestone deposited on the ocean floor between 635 million and 715 million years ago. This period was marked by two “Snowball Earth” events, when ice may have covered the entire planet. …[snip]…

Australian scientists have discovered an ancient reef that may push back the evolution of the earliest animals by 80 million years.

The unpublished research, by geoscientists Associate Professor Malcolm Wallace, Estee Woon and Jonathan Giddings from the University of Melbourne, will be presented at the Geological Society of Australia’s Selwyn Symposium on Thursday.

The researchers say they have uncovered complex organisms that in some ways resemble multicellular life in a large reef located in the Northern Flinders Ranges, 700 kilometres north of Adelaide in South Australia.

If the fossils, which are around 650 million years old, are of multicellular organisms, they would be the earliest examples of primitive animal life discovered so far, the researchers say. … [snip]…

Paris – Organisms long thought to have been the ancestors of early marine creatures may in fact have lived on land, said a fossil study on Wednesday that may prompt an overhaul of the tree of animal life.

If correct, the finding could challenge the commonly held theory that life had thrived in the oceans for hundreds of millions of years before spreading to land.

The fossils, dubbed Ediacaran and dated to 542-635 million years ago, were unearthed in south Australia in 1946, and were long thought to have been the remains of jellyfish, worms and flowery seafloor-dwelling creatures known as sea pens.

Now a geological scientist from the University of Oregon, using state-of-the-art chemical and microscopic analysis techniques, has concluded the fossils more likely belonged to land-dwelling organisms and were not animals at all. … [snip]…

Home / News / News item Animal ancestors may have survived ‘snowball Earth’
Chemical fossils push back the date for animal life to at least 635 million years ago
By Rachel Ehrenberg

A new analysis of ancient chemical fossils has rocked the cradle of early animal evolution, bumping back compelling evidence of animal life to at least 635 million years ago.

The findings, published in the Feb. 5 Nature, suggest that the ancient ancestor of fully formed animals survived a massive glaciation that enshrouded the Earth in ice at the end of the aptly named Cryogenian period. Debate continues over how much of the planet was frozen during two ice ages, each possibly a “snowball Earth” event that flanked this period, which extended from about 790 million to 630 million years ago. … The new work fits nicely with molecular clock work dating the evolution of multicellular life, says Peterson. It also ties in well with ideas about ocean and atmospheric chemistry. These early sponges might have helped bring about the oxygenation of the deep oceans, which then paved the way for more life. Sponges are a dominant stationary animal in the Cambrian, but then their presence seems to taper off, perhaps because of the rise of other animals.

“Sponges are essentially vacuum cleaners; they suck the organic matter out of the world’s oceans,” Peterson says. Amounts of organic matter, the organic form of carbon, are linked to a complex cycle that includes oxygen.

Brock agrees. “Sponges might have filtered all the crap away, might have been the cleaner of the oceans,” he says. “It’s an interesting idea. In total this is a very nice finding, rigorous work and a good job.”

Interesting. I had thought an alternative view for the delay in the rise of accessible oxygen was that it was being captured by iron, which then precipitated to form the massive ‘banded iron’ formations. O2 levels could start to rise when sufficient amounts of iron had precipitated out of the oceans.

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